Chemically amplified positive type resist compositions are a pattern forming material in which upon irradiation with a radiation such as far ultraviolet rays, an acid is formed in exposed areas, and reaction of the acid with a catalyst changes solubility of irradiated areas and non-irradiated areas with active a radiation against a developing solution, thereby forming a pattern on a board.
In the case where a KrF excimer laser is used as an exposure light source, since a resin comprising, as a basic skeleton, poly(hydroxystyrene) exhibiting small absorption mainly in a region of 248 nm is used as the major component, the resulting system has high sensitivity and high resolution and forms a good pattern, and becomes a good system as compared with the conventional naphthoquinonediazide/novolak resin systems.
However, in the case where a light source of a shorter wavelength, such as an ArF excimer laser (193 nm), is used as the exposure light source, since an aromatic group-containing compound essentially exhibits large absorption in a region of 193 nm, even the foregoing chemically amplified systems were not satisfactory.
Utilization of a poly(meth)acrylate as a polymer exhibiting small absorption in the wavelength region of 193 nm is described in J. Vac. Sci. Technol., B9, 3357 (1991). However, there was a problem that this polymer is low in resistance to dry etching that is generally carried out in the manufacture step of semiconductors as compared with the conventional aromatic group-containing phenol resins.
JP-A-2000-159758 discloses a resist for ArF excimer laser containing a resin having a specific lactone structure. However, the conventional resists for ArF excimer laser involved a problem such that the sensitivity fluctuates with time.
Also, the conventional resists for ArF excimer laser involved a problem in spreading property of a developing solution during development (easiness in spreading of a developing solution during development). That is, in the conventional resists for ArF excimer laser, there was some possibility that the resist film repels the developing solution during development. For this reason, there was a problem that the developing solution falls down from a silicon wafer during spreading of the developing solution, thereby wasting the developing solution. This problem becomes remarkable with the advance of enlargement in size of a silicon wafer to be used. Therefore, there have been demanded resists in which the developing solution can be spread more smoothly within a short period of time.